In U.S. Pat. No. 2,740,243, there is disclosed a vacuum packaging apparatus of such arrangement that a multiplicity of chambers are movable integrally with a large circular table which is rotatable on its center portion as a rotation axis, each of the chambers being adapted to be separated from the table at a predetermined position, whereby if a foodstuff loaded bag is supplied to the underside of the chamber at the position at which the chamber is off the table, the foodstuff in the bag is caused to move integrally with the table and a vacuum atmosphere is created around the foodstuff before the foodstuff returns to its original position, the mouth of the bag being heat-sealed sealed in the vacuum atmosphere.
Another arrangement is disclosed in U.S. Pat. No. 2,958,391 such that a multiplicity of square tables are moved along an ellipsoidal track having a circular track portion at one side and chambers are sequentially placed on individual tables at the circular track portion so that foodstuffs are vacuum packaged within individual hermetic spaces defined between the table and the chambers.
Another vacuum packaging apparatus is disclosed in U.S. Pat. No. 4,538,399 wherein four tables and four chambers are rotated along a circular track so that foodstuff is vacuum packaged in each of the individual chambers while the tables and the chambers are in their rotational movement along the circular track.
In all these vacuum packaging apparatuses, the upper surface of the table is flatly configured to facilitate sliding of goods thereon so that foodstuff can be easily set in position under each chamber even when the table is in continuous rotation, while on the other hand vacuum packaged goods can be removed from the table comparatively easily. Therefore, the apparatuses are well suited for the purpose of high efficiency vacuum packaging of, for example, comparatively heavy cut pieces of meat.
In operation of such vacuum packaging apparatus, as the chambers are lifted and separated from the table, vacuum packaged goods on the table are removed therefrom and then a fresh supply of cut pieces of meat contained in bags is delivered to the table. Thereupon, the chambers are lowered onto the table for contact therewith; and a vacuum atmosphere is gradually created around the cut pieces of meat, the mouth of each bag being then heat sealed. The heat sealed mouth of each bag is allowed to become solidified by natural drying or forced drying and then air is introduced into the chambers for separation thereof from the table. This series of operation is repeated for each turn of the table around the endless track. The speed of rotation of the table and chambers is set to the maximum permissible limit so that the series of operation is carried out efficiently and without loss of time in the course of one turn of the table.
However, a close examination of the foregoing series of operation reveals that the operation of discharging vacuum packaged goods from the table after air is introduced into the chambers, with time allowed for the chambers, which are rather heavy, being lifted and separated from the table, leaves some room for improvement from the standpoint of operation efficiency. When introduction of air into each chamber begins, the atmosphere acting on the chamber operates to urge the chamber against the table; therefore, if there is any slight pressure difference between the interior of the chamber and its exterior, the chamber cannot be separated from the table, and only when the pressure difference is completely gone, the chamber can be removed from the table. Further, the chamber, if it is heavy, cannot be rapidly separated from the table, and as such, relatively long time is required after introduction of air into the chamber begins and until vacuum packaged goods on the table are removed from the table.